<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>首页</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            margin: 0;
            background-color: #f9f9f9;
        }
        .button-group {
            margin: 10px;
        }
        .button-group button {
            display: block;
            margin: 5px 0;
            padding: 10px 20px;
            font-size: 16px;
            cursor: pointer;
            background-color: #007bff;
            color: white;
            border: none;
            border-radius: 5px;
        }
        .button-group button:hover {
            background-color: #0056b3;
        }
    </style>
</head>
<body>
<div>
    <div class="button-group">
        <h3>Level 1</h3>
        <button onclick="window.location.href='level1/1.html'">Level 1 - 1</button>
        <button onclick="window.location.href='level1/2.html'">Level 1 - 2</button>
    </div>
    <div class="button-group">
        <h3>Level 2</h3>
        <button onclick="window.location.href='level2/1.html'">Level 2 - 1</button>
        <button onclick="window.location.href='level2/2.html'">Level 2 - 2</button>
    </div>
</div>
</body>
</html>